In recent years, in optical components used for products such as a display and a lighting device, it is desirable to realize a device having the expression of an unprecedented new function which controls reflection and diffraction of light by forming a fine pattern (from nanometer (nm) order to micron (μm) order) exerting particular optical characteristics. As methods for forming the fine pattern, an imprinting technique is attracting attention recently in addition to a photolithography technique and an electron beam lithography technique. The imprinting technique is a technique of transferring the fine pattern of a mold by pressing the mold in which the fine pattern is formed on the surface onto a transferred object.
As specific methods, there are a thermal imprinting method and a UV imprinting method. The thermal imprinting method includes a process of applying a thermoplastic resin as a transferred object on a substrate and heating the thermoplastic resin to be higher than a glass transition temperature to soften the thermoplastic resin, a process of pressing a mold onto the softened thermoplastic resin to transfer the fine pattern of the mold and a process of cooling the thermoplastic resin to be cured.
The UV imprinting method includes a process of applying a UV curing resin as a transferred object on a substrate and pressing a mold onto the uncured UV curing resin to transfer the fine pattern of the mold and a process of curing the UV curing resin by irradiating the UV curing resin with a UV light while pressing the mold.
Although the thermal imprinting method has an advantage that the selectivity in the material of the transferred object is wide, there is a disadvantage that the throughput is low as the heating process and the cooling process of the thermoplastic resin are necessary. On the other hand, in the UV imprinting method, the selectivity in the material is narrower than that of the thermal imprinting method as the material of the transferred object is limited to the UV curing resin. However, the heating process and the cooling process are not necessary and the transfer can be completed for several seconds to several tens of seconds, therefore, the throughput is extremely high. Which of the thermal imprinting method and the UV imprinting method is adopted depends on devices to which the method is applied. The UV imprinting method is considered to be suitable for the mass production method when there is no problem caused by the material.
As a method of forming the fine pattern, a flat-plate imprint is in common use, in which a flat-plate mold 30 in which a fine pattern 33 is formed is vertically pressurized with respect to a resin 70 applied on a surface of a substrate 71 to thereby transfer the fine pattern 33 of the mold 30 to the resin 70 as shown in FIG. 9.
However, as a surface of the mold 30 contacts a surface of the resin 70 in this method, it is highly likely that microbubbles remain inside the fine pattern 33 of the mold 30 and that a transfer defect occurs. In order to inhibit the transfer defect due to the bubbles, it is necessary to perform the imprinting under a vacuum environment. In that case, there are problems that costs for a vacuum apparatus are required and that the throughput is reduced as a fixed period of time is necessary for allowing the apparatus to reach a given degree of vacuum.
In JP-A-2014-54735 (Patent Document 1), a roll-type UV imprinting method as shown in FIG. 10 is adopted for solving the above problems. In this method, the thin-plate mold 30 in which the fine pattern 33 is formed is fed in a feeding direction X while pressurizing the mold 30 with respect to the UV curing resin 70 applied to the substrate 71 by a pressing roll 10, thereby sequentially transfer the fine pattern 33 of the mold 30 to the UV curing resin 70. The UV curing resin 70 is cured by being irradiated with a UV light 61 by a UV irradiator 60 installed behind the pressing roll 10.
In this method, the mold 30 is sequentially pressed onto the substrate 71 by moving the pressing roll 10, therefore, the air is easily released to the feeding direction X of the pressing roll 10 and the fine pattern 33 of the mold 30 can be formed without trapping the air inside the fine patterns 33. Furthermore, as a pressed area between the mold 30 and the substrate 71 has a line shape, the pressure for the transfer can be reduced. Additionally, as the processing can be performed under atmospheric pressure, a large-scale vacuum apparatus is not required.